2012 Dodge Ram 6.7L Cummins No Start

Turn key to start and the motor bumps over and starter disengages. Continue holding key in start position and wait a few seconds and it will bump again. Will never completely turnover. New batteries. Does anyone have any ideas?

So your saying the engine isn’t actually turning over?? It’s just a small bump?? If so I’d be tempted to check block grounds and voltage drop the power feed to the starter

I agree with Cheryl. Voltage checks at the B+ starter cable, solenoid and block ground are in order.

If the PCM is taking the starter solenoid circuit away, then we need to ask why.

A specific type of battery fault called a dead cell can sometimes do that but it really sounds like a cable terminnal issue either the main ground or the main bat+ but it could also be an ignitionswitch or a starter solenoid issue.
If you have a multimeter you can check the voltage drops.

(1) Check the battery voltage between the Bat + and Bat - (directly at battery) with the ignition off and when operating the starter the voltage should be around 12.5v with starter off and around 10.5 when cranking. If the voltage drops quickly below 10 volts to 6 volts or drops to 6 volts and then starts to rise again you have a bad cell in the battery.

(2) Check voltage between the cylinder block and the battery Bat - when operating the starter. With starter being operated it should read below about 200mv. There is a quick and dirty alternative way of doing an equivalent test by simply taking a booster cable between the battery B - and the a good ground on the cylinder block.

(3) You next need to use the multimeter to check the voltage drop between the Battery B+ and the B+ (the large diameter cable) on the starter when the starter is operated, again look for a drop less than 200mv.